Radiation imaging apparatus, computed tomography apparatus, and radiation imaging method

ABSTRACT

A radiation imaging apparatus includes: a radiation emitter configured to emit radiation toward an object and to move around the object at a same time; a radiation detector configured to detect the radiation emitted from the radiation emitter, to change the detected radiation into a signal, and to store the signal; and an irradiation controller configured to control the radiation emitter so that the radiation is emitted toward the object in a first position around the object and so that no radiation is emitted toward the object in a second position corresponding to the first position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 13/946,381 filed on Jul.19, 2013, which claims priority from Korean Patent Application No.10-2012-0131082 filed on Nov. 19, 2012, and Korean Patent ApplicationNo. 10-2013-0046722 filed on Apr. 26, 2013, in the Korean IntellectualProperty Office, the entire disclosures of which are incorporated hereinby reference.

BACKGROUND

1. Field

Exemplary embodiments relate to a radiation imaging apparatus, acomputed tomography apparatus, and a radiation imaging method using thesame.

2. Description of the Related Art

A radiation imaging apparatus, such as a Digital Radiography (DR)system, a Computed Tomography (CT) apparatus, a Full Field DigitalMammography (FFDM) apparatus, or the like, is an imaging system thatemits radiation, e.g., X-rays (also referred to as Roentgen rays) to anobject, such as a human body or a part thereof or luggage, therebyacquiring an image of the object, for example, an image of internalmaterials, tissues or structures of the object.

The radiation imaging apparatus may be used in a medical imaging systemto detect any diseases or other abnormalities of a human body, may beused to observe internal structures of components, and may be used as ascanner to scan luggage in the airport, etc.

A CT apparatus is adapted to acquire a plurality of cross-sectionalimages of an object by continuously emitting radiation to the objectfrom around the object throughout 360 degrees and detecting radiationhaving passed through the object. To acquire successive cross-sectionalimages, the CT apparatus continuously emits radiation to the object,e.g., a human body from the beginning to the end of imaging.

SUMMARY

It is an aspect to provide a radiation imaging apparatus, a computedtomography apparatus, and a radiation imaging method, which enableacquisition of radiological images of an entire object via emission ofradiation to the object in some directions or zones in the vicinity ofthe object.

It is another aspect to provide a computed tomography apparatus whichenables generation of successive cross-sectional images of an object viaradiation emission in some positions or zones.

It is a further aspect to considerably reduce radiation exposure of anobject via radiation emission in some directions or zones.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be obvious from the description.

In accordance with one aspect, a radiation imaging apparatus includes aradiation emitter to emit radiation to an object while moving around theobject, a radiation detector to detect radiation emitted from theradiation emitter and change the detected radiation into an electricsignal to thereby store the electric signal, and an irradiationcontroller to control the radiation emitter such that radiation isemitted to the object in at least one position around the object andsuch that no radiation is emitted to the object in a positioncorresponding to the at least one position.

The irradiation controller may control the radiation emitter such thatthe radiation emitter emits radiation to the object if the radiationemitter is located in the at least one position around the object andsuch that the radiation emitter stops radiation emission if theradiation emitter is located in a position opposite to the at least oneradiation emission position.

The radiation imaging apparatus may further include an image processorto read out a radiological image from the electric signal changed by theradiation detector.

The image processor may generate at least one radiological imagecaptured in a direction opposite to a radiation emission direction basedon a single radiological image captured in the radiation emissiondirection.

The radiation emitter may move around the object at a preset angularspeed. In this case, the irradiation controller may determine whether ornot to perform radiation emission by the radiation emitter based on theangular speed of the radiation emitter, and may control radiationemission by the radiation emitter based on the determined result. Inaddition, the irradiation controller may control the radiation emittersuch that the radiation emitter stops radiation emission when anirradiation duration has passed after radiation emission has begun, andsuch that the radiation emitter initiates radiation emission after anon-irradiation duration has passed after radiation emission hasstopped.

The radiation imaging apparatus may further include a filter installedin a radiation emission path, along which radiation is emitted by theradiation emitter, to pass or block radiation emitted from the radiationemitter. Here, the irradiation controller may control the filter suchthat the filter passes radiation emitted from the radiation emitter ifthe radiation emitter reaches a given position while moving around theobject and such that the filter blocks radiation emitted from theradiation emitter if the radiation emitter reaches a position or zoneopposite to the given position about the object.

In accordance with another aspect, a radiation imaging apparatusincludes a radiation emitter configured to move along a movement pathdefined around an object and to emit radiation to the object duringmovement thereof, and a radiation detector to receive radiation emittedfrom the radiation emitter and change the received radiation into anelectric signal, wherein the movement path defined around the object isdivided into at least one irradiation zone in which the radiationemitter emits radiation, and at least one non-irradiation zone in whichthe radiation emitter does not emit radiation, and the non-irradiationzone is located opposite to the at least one irradiation zone.

The radiation imaging apparatus may further include an image processorto generate a radiological image by combining at least one radiologicalimage generated via detection of radiation emitted in the at least oneirradiation zone.

The image processor may generate a radiological image of thenon-irradiation zone opposite to the irradiation zone based on theradiological image of the irradiation zone.

The irradiation zone or the non-irradiation zone may be determined by anarc between at least two positions on the movement path.

The irradiation zone and the non-irradiation zone on the movement pathmay be alternatingly arranged.

The radiation emitter may be moved along the movement path definedaround the object at a preset angular speed.

The radiation imaging apparatus may further include an irradiationcontroller to control the radiation emitter such that the radiationemitter initiates radiation emission when entering the irradiation zoneand stops radiation emission when entering the non-irradiation zone.

The radiation emitter may be moved along the movement path definedaround the object at a preset angular speed, and the irradiationcontroller may determine whether or not to perform radiation emission bythe radiation emitter based on the angular speed of the radiationemitter, and may control radiation emission by the radiation emitterbased on the determined result.

The irradiation controller may control the radiation emitter such thatthe radiation emitter stops radiation emission when an irradiationduration has passed after radiation emission has begun, and such thatthe radiation emitter initiates radiation emission after anon-irradiation duration has passed after radiation emission hasstopped.

In accordance with another aspect, a radiation imaging apparatusincludes a radiation emitter configured to move along a movement pathdefined around an object and to emit radiation to the object, a filterinstalled in a radiation emission path, along which radiation is emittedby the radiation emitter, to pass or block radiation emitted from theradiation emitter, and a radiation detector to receive radiation emittedfrom the radiation emitter and change the received radiation into anelectric signal, wherein the filter passes radiation emitted from theradiation emitter in at least one irradiation position or irradiationzone on the movement path, and blocks radiation emitted from theradiation emitter in at least one non-irradiation position ornon-irradiation zone corresponding to the at least one irradiationposition or irradiation zone.

The radiation imaging apparatus may further include an image processorto read out a radiological image from the electric signal changed fromthe radiation emitted in the at least one irradiation position orirradiation zone. The image processor may generate a radiological imageof the at least one non-irradiation position or non-irradiation zonebased on the radiological image of the at least one irradiation positionor irradiation zone.

The irradiation position or irradiation zone and the non-irradiationposition or non-irradiation zone on the movement path may bealternatingly arranged.

The movement path defined around the object may be circular or spiral.

The filter may include at least one opening to pass radiation.

The filter may rotate about a rotating shaft located inside or outsideof the filter. In this case, the filter may rotate at an angular speedcorresponding to an angular speed of the radiation emitter that movesalong a circular or spiral movement path. In addition, the angular speedof the filter may be determined based on the number of openings formedin the filter to pass radiation, the angular speed of the radiationemitter, the number of times radiation is emitted while the radiationemitter rotates once, or the size of the irradiation zone or thenon-irradiation zone.

In accordance with another aspect, a radiation imaging apparatusincludes a radiation emitter configured to move around an object atleast one time and to generate radiation upon receiving power appliedthereto and emit the generated radiation to the object, a radiationdetector configured to move around the object at least one timeaccording to movement of the radiation emitter and to detect radiationemitted from the radiation emitter and change the detected radiationinto an electric signal to thereby store the electric signal, and anirradiation controller to control application or interception of powerto the radiation emitter, wherein the irradiation controller performsapplication and interception of power to the radiation emitter pluraltimes while the radiation emitter and the radiation detector move aroundthe object once.

In accordance with another aspect, a radiation imaging apparatusincludes a radiation emitter configured to move around an object and toemit radiation to the object, a radiation detector to detect radiationemitted from the radiation emitter and change the detected radiationinto an electric signal to thereby store the electric signal, and anirradiation controller to control the radiation emitter such thatradiation is emitted to the object in a given direction of the objectand such that no radiation is emitted to the object in a directioncorresponding to the given direction in which radiation is emitted tothe object.

In accordance with another aspect, a computed tomography apparatusincludes a rotatable gantry, a radiation emitter installed at one sideof the gantry to emit radiation to an object, a cradle on which theobject is placed, the cradle being moved into the gantry, and aradiation detector installed to the gantry at an opposite side of theradiation emitter and serving to receive radiation having passed throughthe object placed on the cradle and change the received radiation intoan electric signal, wherein the radiation emitter emits radiation to theobject in a given direction of the object and does not emit radiation tothe object in a direction opposite to the given direction.

The computed tomography apparatus may further include an irradiationcontroller to control the radiation emitter such that the radiationemitter emits radiation when located in a given position while movingaround the object and to block radiation emission by the radiationemitter when the radiation emitter is located in a positioncorresponding to the given position.

The radiation emitter may move around the object at a preset angularspeed, and the irradiation controller may determine whether or not toperform radiation emission by the radiation emitter based on the angularspeed of the radiation emitter, and may control the radiation emissionby the radiation emitter based on the determined result.

The irradiation controller may stop radiation emission by the radiationemitter when an irradiation duration has passed after radiation emissionhas begun, and may initiate radiation emission by the radiation emitterafter a non-irradiation duration has passed after radiation emission hasstopped.

The radiation emitter may move around the object at a preset angularspeed.

The computed tomography apparatus may further include an image processorto read out a radiological image from the electric signal changed by theradiation detector.

The image processor may generate at least one radiological imagecaptured in a direction opposite to a radiation emission direction basedon a single radiological image captured in the radiation emissiondirection.

The image processor may generate at least one intermediate radiologicalimage between a plurality of radiological images acquired when emittingradiation plural times in the same direction.

The image processor may generate at least one radiological imagecaptured in a direction opposite to a radiation emission direction basedon the generated at least one intermediate radiological image.

In accordance with another aspect, a computed tomography apparatusincludes a rotatable gantry, a radiation emitter installed at one sideof the gantry to emit radiation to an object, a filter installed in aradiation emission direction of the radiation emitter to pass or blockradiation emitted from the radiation emitter, a cradle on which theobject is placed, the cradle being moved into the gantry in a directionperpendicular to the gantry, and a radiation detector installed to thegantry at an opposite side of the radiation emitter and serving toreceive radiation having passed through the object placed on the cradleand change the received radiation into an electric signal, wherein thefilter passes radiation emitted from the radiation emitter in at leastone irradiation position or irradiation zone during movement of thegantry, and blocks radiation emitted from the radiation emitter in atleast one non-irradiation position or non-irradiation zone correspondingto the at least one irradiation position or irradiation zone.

The computed tomography apparatus may further include an image processorto read out a radiological image from the changed electric signal.

The image processor may generate a radiological image with respect toradiation blocked by the filter based on the generated radiologicalimage. More specifically, the image processor may generate at least oneintermediate radiological image between a plurality of radiologicalimages acquired when emitting radiation plural times in the samedirection.

The image processor may generate at least one radiological imagecaptured in a direction opposite to a radiation emission direction basedon the generated at least one intermediate radiological image.

The filter may include at least one opening to pass radiation, and thefilter may rotate about a rotating shaft located inside or outside ofthe filter.

The filter may rotate at an angular speed corresponding to an angularspeed of the gantry, and the angular speed of the filter may bedetermined based on the number of openings formed in the filter to passradiation, the angular speed of the gantry, or the number of timesradiation is emitted while the radiation emitter rotates once.

In accordance with a further aspect, a radiological image acquisitionmethod using a computed tomography apparatus, includes acquiring imagedata in at least one irradiation position or zone by emitting radiationto an object when a radiation emitter reaches the irradiation positionor zone, stopping radiation emission when the radiation emitter reachesat least one non-irradiation position or zone, and acquiring a pluralityof image data in a plurality of irradiation positions or zones byrepeating acquisition of the radiological image data and stop of theradiation emission, wherein the at least one irradiation position orzone and the at least one non-irradiation position or zone may bearranged to correspond to each other.

The radiological image acquisition method may further includecalculating at least one image data captured in the non-irradiation zonebased on at least one image data acquired in the at least oneirradiation zone among the plurality of acquired image data.

The radiological image acquisition method may further include passingradiation emitted to the object through the filter if the radiationemitter reaches the at least one irradiation zone, and blockingradiation emitted to the object by the filter if the radiation emitterreaches the at least one non-irradiation zone, and the at least oneirradiation zone may be located to correspond to the at least onenon-irradiation zone.

In an exemplary embodiment, there is a radiation imaging apparatusincluding: a radiation emitter configured to emit radiation toward anobject and to move around the object at a same time; a radiationdetector configured to detect the radiation emitted from the radiationemitter, to change the detected radiation into a signal, and to storethe signal; and an irradiation controller configured to control theradiation emitter so that the radiation is emitted toward the object ina first position around the object and such that no radiation is emittedtoward the object in a second position corresponding to the firstposition.

In yet another exemplary embodiment, there is a radiation imagingapparatus including: a radiation emitter configured to move along a pathabout an object in a movement and to emit radiation toward the objectduring the movement; and a radiation detector configured to receive theradiation emitted from the radiation emitter and to change the receivedradiation into a signal, wherein the path about the object is dividedinto at least one irradiation zone in which the radiation emitter emitsthe radiation, and at least one non-irradiation zone in which theradiation emitter does not emit the radiation, and the at least onenon-irradiation zone is located opposite to the at least one irradiationzone.

In one exemplary embodiment, there is a radiation imaging apparatusincluding: a radiation emitter configured to move along a first pathabout an object and to emit radiation toward the object; a filterdisposed in a second path along which the radiation is emitted by theradiation emitter, to pass or to block the radiation emitted from theradiation emitter; and a radiation detector configured to receive theradiation emitted from the radiation emitter and to change the receivedradiation into a signal, wherein the filter passes the radiation emittedfrom the radiation emitter in at least one irradiation position orirradiation zone on the first path, and blocks the radiation emittedfrom the radiation emitter in at least one non-irradiation position ornon-irradiation zone corresponding to the at least one irradiationposition or irradiation zone.

In yet another exemplary embodiment, there is a radiological imageacquisition method using a computed tomography apparatus, the methodincluding: performing a radiation imaging operation to acquire aplurality of radiological image data in a plurality of directions bycontrolling a radiation emitter so that radiation is emitted toward anobject in at least one direction around the object and so that noradiation is emitted toward the object in a direction corresponding tothe at least one direction; and performing an image data combinationoperation to combine the plurality of radiological image data in theplurality of directions.

In one exemplary embodiment, there is a radiation imaging apparatusincluding: an emitter configured to simultaneously emit radiation towardan object and to move around the object; a detector configured to detectthe radiation passing through the object, to convert the detectedradiation into a signal, and to store the signal; and means fordetermining a location of the emitter or detector; a controllerconfigured to control the radiation emitter based on the location of theemitter or detector detected by the means for determining, to emit theradiation toward the object when the location is at a first position andto not emit the radiation toward the object when the location is at asecond position that is opposite to the first position.

In another exemplary embodiment, there is a radiation imaging apparatusincluding: an emitter configured to simultaneously emit radiation towardan object and to move around the object; means for shuttering theradiation emitted by the emitter; a detector configured to detect theradiation passing through the means for shuttering and the object, toconvert the detected radiation into a signal, and to store the signal;and a controller configured to control the means for shuttering based ona location of the emitter or detector.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the exemplary embodiments,taken in conjunction with the accompanying drawings of which:

FIG. 1 is a view illustrating a whole configuration of a radiationimaging apparatus according to an exemplary embodiment;

FIG. 2 is a view illustrating a radiation emitter according to anexemplary embodiment;

FIGS. 3A, 3B, 3C, 3D, and 3E are views explaining radiation emission bythe radiation emitter on a movement path according to an exemplaryembodiment;

FIGS. 4A, 4B, and 4C are views explaining radiation emission by theradiation emitter on a movement path according to another exemplaryembodiment;

FIGS. 5A, 5B, 5C, and 5D are views illustrating an exemplary embodimentof a filter;

FIGS. 6A and 6B are views illustrating another exemplary embodiment ofthe filter;

FIGS. 7A, 7B, and 7C are views illustrating various exemplaryembodiments of the filter;

FIG. 8 is a view explaining emission of radiation to an object accordingto an exemplary embodiment;

FIG. 9 is a view illustrating a radiation detector according to anexemplary embodiment;

FIGS. 10A, 10B, and 10C are a perspective view and explanatory views ofa collimator installed to the radiation detector;

FIGS. 11A and 11B are views illustrating a configuration of an imageprocessor according to several exemplary embodiments;

FIGS. 12A, 12B, and 12C are views respectively illustrating radiationemission in different directions and radiological images acquired byradiation emission;

FIGS. 12D, 12E, and 12F are views respectively illustrating a spatialdomain and a frequency domain acquired by the radiation imagingapparatus;

FIG. 13 is a view illustrating a configuration of a computed tomographyapparatus;

FIGS. 14, 15, and 16 are views illustrating a configuration of acomputed tomography apparatus;

FIGS. 17 and 18 are views explaining radiography by the computedtomography apparatus;

FIGS. 19, 20, and 21 are views illustrating another exemplary embodimentof the computed tomography apparatus;

FIGS. 22A, 22B, and 22C are views explaining generation of radiologicalimages according to an exemplary embodiment;

FIGS. 23, 24, and 25 are views explaining an exemplary embodiment of aFull Field Digital Mammography (FFDM) apparatus; and

FIGS. 26 and 27 are flowcharts illustrating various exemplaryembodiments of a radiological image generation method.

DETAILED DESCRIPTION

Reference will now be made in detail to the exemplary embodiments,examples of which are illustrated in the accompanying drawings, whereinlike reference numerals refer to like elements throughout.

FIG. 1 is a view illustrating a whole configuration of a radiationimaging apparatus according to an exemplary embodiment.

As illustrated in FIG. 1, according to the exemplary embodiment, theradiation imaging apparatus includes a radiation emitter 10 and aradiation detector 20. The radiation emitter 10 emits radiation, e.g.,X-rays to an object ob. It is noted that the invention is not limited tothe radiation emitter 10 which emits X-rays but also contemplates theuse of other emitters which output emissions in the electromagneticspectrum, other than X-rays. The radiation detector 20 receivesradiation that has passed through the object ob or radiation directed tothe vicinity of the object ob, and changes the received radiation intoan electric signal for storage of the electric signal or into anelectrical signal that is representative of radiation information or aradiological image which is subsequently stored.

The radiation imaging apparatus, as exemplarily illustrated in FIG. 1,may further include an image processor 30 that reads out a radiologicalimage from the electric signal stored in the radiation detector 20.Alternatively, the image processor 30 reads out the radiationinformation or the radiological image stored in the radiation detector20. The image processor 30 may process the generated radiological image,or may generate an additional radiological image using the generatedradiological image.

The radiation imaging apparatus may further include an irradiationcontroller 40 to control whether or not to perform radiation emission bythe radiation emitter 10, e.g., to control the emission of radiation bythe radiation emitter 10. In one exemplary embodiment, the irradiationcontroller 40 controls the radiation emitter 10 to achieve such control.

Additionally, the radiation imaging apparatus may include a movementcontroller 50 to control movement of the radiation emitter 10, forexample, rotational movement around the object ob. In another exemplaryembodiment, the movement may be curved, arcuate, curvilinear, linear, orstepped. The movement controller 50 also controls movement of theradiation emitter 10 and the radiation detector 20. The movement of theradiation emitter 10 may correspond to the movement of the radiationdetector 20. In one exemplary embodiment, the movement of the radiationemitter 10 may be matching, symmetric, synchronous, approximatelymatching, approximately symmetric, or approximately synchronous withrespect to the movement of the radiation detector.

Functions of the image processor 30, the irradiation controller 40, andthe movement controller 50 may be performed by a processor such as aCentral Processing Unit (CPU) or a separate information processingdevice provided in the radiation imaging apparatus.

The radiation imaging apparatus may further include a cradle 61 on whichthe object ob is placed as illustrated in FIG. 1. The cradle 61 may bemovable according to exemplary embodiments. In one embodiment, thecradle is a patient table.

Specifically, the radiation emitter 10 may emit radiation to the objectob while moving along a movement path r1 around the object ob. In thisexemplary embodiment, the movement path r1, for example, may be an ovalpath or a circular path as exemplarily illustrated in FIG. 1. Althoughthe movement path r1 may or may not be predetermined. In one example,the movement path r1 may be a part of a circle or oval, or may have anarc shape. As such, the radiation emitter 10 may emit radiation to theobject ob while moving around the object ob along the circular, oval, orarc-shaped movement path r1 spaced apart from the object ob by apredetermined distance. However, the movement path r1 is not limited tocircular or oval shapes, but may have other shapes, including thosedisclosed above.

The radiation emitter 10, according to exemplary embodiments, may emitradiation having different energy-bands to the object ob. This mayenable acquisition of multi-energy X-ray (MEX) images.

The radiation detector 20 may move along a movement path r2 similar tothe radiation emitter 10, so as to receive radiation emitted from theradiation emitter 10. Likewise, the movement path r2 may or may not bepredetermined. In this case, the movement path r2 of the radiationdetector 20 may have the same shape as the movement path of theradiation emitter 10. For example, as exemplarily illustrated in FIG. 1,the movement path r2 of the radiation detector 20 may be circular in thesame manner as in the radiation emitter 10. In addition, the movementpath r2 of the radiation detector 20 may have an oval shape, or may havean arc shape. The radiation detector 20 functions to detect radiationemitted from the radiation emitter 10 while moving along the circular,oval, or arc-shaped movement path r2 and to change the detectedradiation into an electric signal to store the electric signal therein.However, the movement path r2 is not limited to circular or oval shapes,but may have other shapes, including those disclosed above.

According to an exemplary embodiment of the radiation imaging apparatus,the radiation emitter 10 and the radiation detector 20 may be movablyinstalled to an external drive device, e.g., a gantry of a computedtomography apparatus. That is, the radiation emitter 10 and theradiation detector 20 may be circularly movable around the object ob ina predetermined direction via rotation of the gantry of the computedtomography apparatus. During movement around the object ob, theradiation emitter 10 and the radiation detector 20 may be arranged toface each other, to ensure appropriate reception of radiation. In thiscase, the radiation emitter 10 and the radiation detector 20 may havethe same angular speed or angular acceleration, but are not necessarilylimited thereto.

As described above, the movement controller 50 may be provided to movethe radiation emitter 10 and the radiation detector 20.

FIG. 2 is a view illustrating the radiation emitter 10 according to anexemplary embodiment.

As illustrated in FIG. 2, the radiation emitter 10 according to theexemplary embodiment may include a radiation tube 11 to generateradiation, e.g., X-rays, and a power source 12 electrically connected tothe radiation tube 11 so as to apply a voltage to the radiation tube 11.Further, in other exemplary embodiments, the radiation emitter 10 may bean emitter which outputs other emissions in the electromagnetic spectrumother than X-rays.

A method of generating radiation by the radiation emitter 10 will now bedescribed by way of example.

If the power source 12 of the radiation emitter 10 applies apredetermined voltage to the radiation tube 11, electrons areaccelerated in a cathode filament 111 of the radiation tube 11 accordingto the voltage applied thereto to thereby move toward an anode 112. Uponreaching the anode 112, the accelerated electrons are rapidly reduced inspeed near an atomic nucleus of the anode 112. In this case, radiation,e.g., X-rays are generated in the anode 112 according to the principleof energy conservation.

The radiation generated in the anode 112 is not essentially directedonly in a direction and range that the user desires. Also, even ifradiation is directed in a direction that the user desires, it may benecessary to reduce an emission range, for example, if an object issmall or when it is desired to emit radiation to only a local part of anobject. Therefore, to control a radiation emission direction andradiation emission range, for example, to control a wider or narroweremission range, according to an exemplary embodiment, a first collimator13 may be installed on a radiation emission path from the radiation tube11.

The collimator 13 assists the user in controlling a radiation emissiondirection and a radiation emission range by filtering and guiding aplurality of radiation into a particular direction and a predeterminedrange. The collimator 13 includes at least one collimator blade orcollimator filter formed of a material capable of absorbing radiation,for example, lead (Pb).

In one example, as exemplarily illustrated in FIG. 2, some radiation x1and x2 generated in the anode 112 and directed in a direction that theuser does not desire are absorbed by, e.g., a partition 131 of the firstcollimator 130 so as not to be directed to the object ob, and radiationx3 directed in a direction that the user desires is directed toward theobject ob through, e.g., an opening 132 of the first collimator 130.

In the case in which the radiation imaging apparatus is a computedtomography apparatus, the first collimator 130 may allow radiationgenerated by the radiation tube 11 to be directed in a fan shape orother shapes to the object ob.

The radiation emitter 10, as described above in FIG. 1, may emitradiation to the object ob while moving along a movement path around theobject ob. In this case, the radiation emitter 10, according to anexemplary embodiment, may selectively emit radiation to the object obfor a period or according to a position on the movement path where theradiation emitter 10 is located. According to another exemplaryembodiment, the radiation emitter 10 may continuously emit radiation tothe object ob.

FIGS. 3A to 3E are views explaining radiation emission by the radiationemitter on a movement path according to an exemplary embodiment.

According to an exemplary embodiment of the radiation imaging apparatus,the radiation emitter 10 may emit radiation to the object ob only in aposition or zone on a movement path thereof. The position or zone may ormay not be predetermined. According to an exemplary embodiment, if theradiation emitter 10 emits radiation to the object ob in a position orzone as exemplarily illustrated in FIG. 3A, the radiation emitter 10 maynot emit radiation to the object ob in a position or zone correspondingto the position or zone where the radiation emitter 10 emits radiationto the object ob. More specifically, the position or zone correspondingto the position or zone where radiation emission occurs may be aposition or zone opposite to the position or zone about a point, anaxis, or a point of reference, all of which may be predetermined or maynot be predetermined. For example, the position or zone corresponding tothe position or zone where radiation emission occurs may be a positionor zone located in an opposite direction about the object ob. Inaddition, the position or zone corresponding to the position or zonewhere radiation emission occurs may be an opposite position or zone ofthe position or zone about the axis.

For example, as illustrated in FIG. 3A, the radiation emitter 10 mayemit radiation to the object ob in positions on a movement path thereof,e.g., in a first position 11, a second position 13 and a fifth position15, but may not emit radiation to the object ob in positionscorresponding to the emission positions including the first position 11,the second position 13 and the fifth position 15, i.e. in a fourthposition 14, a sixth position 16 and a second position 12. In otherwords, the object ob may be controlled so as not to receive radiation ina direction corresponding to a radiation emission direction, forexample, in a direction opposite to the radiation emission direction ifthe radiation emitter 10 emits radiation to the object ob in at leastone direction.

The radiation emitter 10, for example, as illustrated in FIG. 3B, mayemit radiation to the object in irradiation zones a1, a3 and a5, but maynot emit radiation to the object ob in non-irradiation zones a2, a4 anda6.

As illustrated in FIG. 3B, in the case in which a movement path of theradiation emitter 10 is a circular path defined around the object ob,the movement path may be divided into the irradiation zones a1, a3 anda5 and the non-irradiation zones a2, a4 and a6. The irradiation zonesa1, a3 and a5 and the non-irradiation zones a2, a4 and a6 may bealternatingly arranged on the movement path so as not to be adjacent tothe same zone. That is, the irradiation zones a1, a3 and a5 arerespectively located at the left side of the respective non-irradiationzones a2, a4 and a6, and in turn the non-irradiation zones a2, a4 and a6are respectively located at the left side of the respective irradiationzones a3, a5 and a1.

In this case, the respective non-irradiation zones a2, a4 and a6 and therespective irradiation zones a1, a3 and a5 are symmetrical to each otheron the circular movement path as exemplarily illustrated in FIG. 3B. Inother words, on the circular movement path, one non-irradiation zone a2,a4 or a6 may be present at an opposite side of one irradiation zone a1,a3 or a5.

According to one exemplary embodiment, the circular movement path may beequally divided. For example, as exemplarily illustrated in FIG. 3B, themovement path may be divided into six zones having the same size. Inthis case, each divided zone may be any one of the irradiation zones a1,a3 and a5 or any one of the non-irradiation zones a2, a4 and a6.

According to another exemplary embodiment, the circular movement pathmay be divided into zones of different sizes. Likewise, each dividedzone may be any one of the irradiation zones a1, a3 and a5 or any one ofthe non-irradiation zones a2, a4 and a6. In this case, thenon-irradiation zones a2, a4 and a6 corresponding to the irradiationzones a1, a3 and a5, or the irradiation zones a1, a3 and a5corresponding to the non-irradiation zones a2, a4 and a6 may have thesame size.

In the case in which the movement path is divided into a plurality ofirradiation zones and non-irradiation zones, the radiation emitter 10initiates emission of radiation to the object ob when entering theirradiation zones a1, a3 and a5 during movement along the movement paththereof. The radiation emitter 10 continuously emits radiation to theobject ob in the irradiation zones a1, a3 and a5, and then stopsradiation emission when entering the non-irradiation zones a2, a4 and a6so as not to emit radiation to the object ob. As a result, radiation isnot emitted to the object ob in the non-irradiation zones a2, a4 and a6.

To allow the radiation emitter 10 to perform radiation emission only ina position or zone, according to an exemplary embodiment, it may bepossible for the radiation emitter 10 to selectively perform radiationemission based on positional information on the radiation emitter 10.

To acquire the positional information on the radiation emitter 10,according to one exemplary embodiment, an angular speed of the radiationemitter 10 may be used. That is, the radiation emitter 10, asillustrated in FIG. 1 or FIG. 3A, may be controlled to perform radiationemission based on an angular speed thereof during movement along acircular movement path thereof.

Through use of the angular speed of the radiation emitter 10, a positionof the radiation emitter 10 after a predetermined duration has passed,i.e. a rotation angle of the radiation emitter 10 after having movedfrom a reference position may be acquired or calculated. The acquiredrotation angle may be used to calculate the position of the radiationemitter 10, and whether or not to perform radiation emission by theradiation emitter 10 may be controlled based on the calculated position.

Additionally, according to another exemplary embodiment, to acquirepositional information on the radiation emitter 10, a position sensormay be used.

To acquire positional information on the radiation emitter 10, anencoder or a detector may be placed on a movement path of the radiationemitter 10 or the radiation detector 20 to detect a position of theradiation emitter 10 or the radiation detector 20. In this case, toallow the encoder to detect a position of the radiation emitter 10 orthe radiation detector 20, the radiation emitter 10 or the radiationdetector 20 may be provided with a detection piece.

If the radiation imaging apparatus is a computed tomography apparatus, adetection piece may be formed at the gantry to which the radiationemitter 10 or the radiation detector 20 is installed, and an encoder,which is installed to a lateral portion of the gantry, may detect thedetection piece on the gantry so as to detect a position of theradiation emitter 10 or the radiation detector 20.

In another exemplary embodiment, a combination of the angular speed andthe detected location of the radiation emitter 10 or the radiationdetector 20 may be used to determine the position of the same.

According to another exemplary embodiment, the radiation emitter 10 mayselectively emit radiation to the object ob for a period or according toa pattern, whereby the period and the pattern may or may not bepredetermined.

The radiation emission interval or pattern may be set or preset by theuser. Of course, to set the radiation emission interval or pattern, theangular speed of the radiation emitter 10 may be used as describedabove.

By using an inverse number of the angular speed of the radiation emitter10, a rotational-movement period of the radiation emitter 10 along acircular movement path may be calculated, and a radiation emissionperiod, i.e. a period for which radiation is emitted and a period forwhich radiation is not emitted may be calculated based on the calculatedperiod. For example, the radiation emission period may be acquired bydividing the calculated period by a 2× multiplied value of the number oftimes radiation is emitted. As such, radiation emission by the radiationemitter 10 may be performed according to the calculated radiationemission period.

To ensure that the radiation emitter 10 emits radiation to the object obin a position or a zone on a movement path thereof, the radiationimaging apparatus, as illustrated in FIG. 1, may include the irradiationcontroller 40. The irradiation controller 40 may control radiationemission by the radiation emitter 10, allowing the radiation emitter 10to selectively emit radiation to the object ob.

The irradiation controller 40, according to one exemplary embodiment,may acquire positional information on the radiation emitter 10, therebycontrolling the radiation emitter 10 so as to selectively performradiation emission according to the acquired positional information onthe radiation emitter 10. In this case, as described above, the angularspeed of the radiation emitter 10 may be used. Also, a separate positionsensor may be used.

The irradiation controller 40, according to another exemplaryembodiment, may control radiation emission by the radiation emitter 10according to a period or pattern, both of which may be or may not bepredetermined. That is, the irradiation controller 40 may allow theradiation emitter 10 to selectively perform radiation emission such thatradiation is emitted only in the irradiation zones a1, a3 and a5according to a period or pattern.

For example, the irradiation controller 40 may control the radiationemitter 10 to stop radiation emission when a emission duration haspassed after radiation emission has begun, and to initiate radiationemission when a duration, i.e. a non-emission duration has passed afterradiation emission has stopped.

Similar to the above description, the irradiation controller 40 maydetermine a radiation emission period using the angular speed of theradiation emitter 10, and control radiation emission based on thedetermined radiation emission period. Alternatively, the irradiationcontroller 40 may control radiation emission using a period or patterninput by the user.

In the exemplary embodiments, the control of the radiation emission maybe based on temporal, spatial, or other factors. In other exemplaryembodiments, calculation of the location of the radiation emitter 10 isnot necessary and mere proximity of the radiation emitter 10 one of anumber of elements would control the radiation emission. The elementswould be selectively controlled in one of two states so that theproximity of radiation emitter 10 to an element in one state would turnon the emission of radiation and the proximity of the radiation emitter10 to another element in another state would turn off the emission ofradiation. The radiation emitter 10 would be in proximity to an elementto be controlled by that element if the radiation emitter 10 is morecloser to that element than other elements or is in contact with thatelement.

To control whether or not to perform radiation emission by the radiationemitter 10, the irradiation controller 40, specifically, may control thepower source 12 of the radiation emitter 10 to allow the power source 12to apply or not apply voltage to the radiation tube 11.

For example, the irradiation controller 40 may generate and transmit acontrol instruction to apply voltage to the radiation tube 11 upondetermining that the radiation emitter 10 enters the irradiation zonesa1, a3 and a5. Alternatively, the irradiation controller 40 may controlapplication of voltage to the radiation tube 11 for a period such thatradiation emission is performed only in the irradiation zones a1, a3 anda5.

Radiation is generated in the anode 112 of the radiation tube 11according to a control instruction for voltage application or accordingto a voltage application period. The radiation emitter 10 emitsradiation to the object ob only in the irradiation zones a1, a3 and a5.

The state of the radiation emitter 10 or the voltage applied to theradiation tube 11 varies as illustrated in FIG. 3C. That is, the stateof the radiation emitter 10 or the applied voltage has a pulsed shape.The state or voltage variation may be performed by the above-describedirradiation controller 40.

For example, as illustrated in FIG. 3C, the irradiation controller 40may transmit an emission instruction or emission-stop instruction to theradiation emitter 10, or may control radiation emission by the radiationemitter 10 on a per period basis, thereby allowing voltage to be applied(Power-On) or to not be applied (Power-Off) to the radiation emitter 10.Since the radiation emitter 10 emits radiation when voltage is appliedthereto, radiation emission is performed in a Power-On state, andradiation emission stops in a Power-Off state.

The On/Off state change may be performed according to a controlinstruction of the irradiation controller 40 or a period as describedabove.

Results of substituting the On/Off state change for a circular movementpath may be illustrated as in FIG. 3D. That is, as illustrated in FIG.3D, the radiation emitter 10 emits radiation to the object ob in aPower-On state of the radiation emitter 10, and stops radiation emissionin a Power-Off state, according to a control instruction or a period.

Although FIGS. 3A to 3D illustrate the case in which the movement pathof the radiation emitter 10 is divided into three or more zones, themovement path may be divided into two equal zones as exemplarilyillustrated in FIG. 3E. That is, as exemplarily illustrated in FIG. 3E,in the case of a circular movement path, the radiation emitter 10 emitsradiation in one half the circular movement path, and does not emitradiation in the other half the circular movement path.

FIGS. 4A to 4C are views explaining radiation emission by the radiationemitter on a movement path according to another exemplary embodiment.

According to another exemplary embodiment of the radiation imagingapparatus, as exemplarily illustrated in FIG. 4A, the radiation emitter10 may continuously generate and emit radiation toward the object ob.That is, the radiation emitter 10 may continuously emit radiation to theobject ob, rather than selectively emitting radiation to the object viaiterative On/Off state change as described above.

According to an exemplary embodiment of the radiation imaging apparatus,when the radiation emitter 10 continuously emits radiation, a filter 14may be provided on a radiation emission path of the radiation emitter10, i.e. in a direction through which the radiation is emitted.

The filter 14 may control emission of radiation to the object ob bypassing or blocking radiation emitted from the radiation emitter 10 whenthe radiation emitter 10 is located in a position or zone.

Specifically, the filter 14 is configured to pass radiation emitted fromthe radiation emitter 10 when the radiation emitter 10 is located in aposition (emission position) or zone (irradiation zone) while movingaround the object ob. On the contrary, when the radiation emitter 10 islocated in an opposite position (non-emission position) or zone(non-irradiation zone) about the object ob, the filter 14 blocksradiation emitted from the radiation emitter 10, thereby controllingemission of radiation to the object ob.

In the case in which the filter 14 is provided in a radiation emissiondirection from the radiation emitter 10, differently from theillustration of FIG. 3C, the radiation emitter 10 may continuouslygenerate and emit radiation after imaging is initiated as illustrated inFIG. 4C. In other words, voltage is continuously applied to theradiation tube 11.

In an exemplary embodiment, the control of the filter 14 is in a mannerthat is the same or similar to the above-mentioned manner of controllingthe emission of radiation by the radiation emitter 10.

FIGS. 5A to 5D are views illustrating an exemplary embodiment of thefilter 14.

According to an exemplary embodiment, as illustrated in FIGS. 5A to 5C,the filter 14 has a disc shape, and an opening 141 for passage ofradiation is formed in a portion of the disc. The opening 141 may have asemi-circular or fan shape according to exemplary embodiments.Additionally, to enable rotation of the disc-shaped filter 14, forexample, a rotating shaft 143 may be provided at the center of the disc.The rotating shaft 143 may be located in another position on the discexcept for the center position, and may be present around the disc.

The filter 14 passes or blocks radiation by rotating about the rotatingshaft 143 in a radiation emission direction from the radiation emitter10. When the opening 141 of the filter 14 is located in a radiationemission path of the radiation emitter 10 during rotation of the filter14, as illustrated in FIG. 5B, the opening 141 passes the radiation.

Conversely, as illustrated in FIG. 5C, if another portion of the filter14 rather than the opening 141, i.e. a radiation blocking portion 142 islocated on the radiation emission path of the radiation emitter 10during rotation of the filter 14, the radiation emitted from theradiation emitter 10 is blocked or absorbed by the filter 14. As such,the radiation emitted from the radiation emitter 10 is controlled by thefilter 14 so as to be selectively emitted to the object ob.

Operation of the filter 14, for example, a movement speed of the filter14, i.e. an angular speed of the filter 14 is set such that the objectob receives emission only within a zone, i.e. within the irradiationzone and does not receive radiation within the other zone, i.e. withinthe non-irradiation zone as illustrated in FIG. 3B.

Specifically, a rotational angular speed of the filter 14 may beadjusted according to a speed of the radiation emitter 10, for example,according to an angular speed of the radiation emitter 10 when theradiation emitter 10 moves along a circular movement path, according tothe size and arrangement of the irradiation zones and non-irradiationzones, and according to the shape or size of the opening 141 of thefilter 14.

For example, assuming that there are six irradiation zones asillustrated in FIG. 5D and that the opening 141 occupies half of thefilter 14 and the blocking portion 142 occupies the other half, arotational angular speed of the filter 14 is set to three times anangular speed of the radiation emitter 10. That is, the rotationalangular speed of the filter 14 is set as represented in the followingEquation 1.

Rotational Angular speed of Filterω₁=Angular speed of Radiation emitterω₂×3  Equation 1

That is, if the radiation emitter 10 moves along the circular movementpath once, the filter 14 may rotate three times.

Once the rotational angular speed of the filter 14 has been set asdescribed above, as illustrated in FIG. 5D, the opening 141 of thefilter 14 is located on the radiation emission path of the radiationemitter 10 when the radiation emitter 10 enters an irradiation zone ((a)of FIG. 5D), thereby allowing radiation emitted from the radiationemitter 10 to reach the object ob. The radiation continuously reachesthe object ob within the irradiation zone ((b) of FIG. 5D).

When the radiation emitter 10 enters the non-irradiation zone ((c) ofFIG. 5D), the blocking portion 142 of the disc except for the opening141 is located on the radiation emission path of the radiation emitter10, thereby blocking radiation to prevent the radiation from reachingthe object ob. The radiation is continuously blocked within thenon-irradiation zone ((d) of FIG. 5D). Then, when the radiation emitter10 again enters the irradiation zone, radiation reaches the object obthrough the opening 141 ((e) of FIG. 5D).

As described above, the rotational angular speed of the filter 14 may beset based on the angular speed of the radiation emitter 10. When theangular speed of the radiation emitter 10 is changed, the rotationalangular speed of the filter 14 is adjusted to correspond to the changedangular speed.

The rotational angular speed of the filter 14 may be adjusted accordingto the size or range of the irradiation zone or the non-irradiationzone. Although the rotational angular speed of the filter 14 may be keptconstant, this may be changed as necessary.

For example, if the non-irradiation zone is longer than the irradiationzone, that is, if an arc length of the non-irradiation zone is longerthan an arc length of the irradiation zone of FIG. 3B, the rotationalangular speed of the filter 14 on the non-irradiation zone may begreater than the rotational angular speed of the filter 14 on theirradiation zone under control. Conversely, if an arc length of thenon-irradiation zone is shorter than an arc length of the irradiationzone of FIG. 3B, the rotational angular speed of the filter 14 on theirradiation zone may be less than the rotational angular speed of thefilter 14 on the non-irradiation zone under control.

The rotational angular speed of the filter 14 may be set based on thesize of the opening 141 of the filter 14. For example, if the opening141 of the filter 14 has about half the size of the disc as illustratedin FIG. 5D, the rotational angular speed of the filter 14 may be threetimes that of the angular speed of the radiation emitter 10 as describedabove.

FIGS. 6A and 6B are views illustrating another exemplary embodiment ofthe filter.

As illustrated in FIG. 6A, the disc-shaped filter 14 may have aplurality of openings, for example, two openings 141 a and 141 b. Inthis case, the filter 14 may less rotate in proportion to the number ofthe openings 141 a and 141 b. Thus, the angular speed of the filter 14may be reduced.

For example, as illustrated in FIG. 6A, it is assumed that there are twoopenings 141 a and 141 b of the filter 14 and the size of each openingis a quarter the size of the disc.

Then, as illustrated in FIG. 6B, if the radiation emitter 10 enters theirradiation zone, any one of the openings 141 a and 141 b of the filter14 is located on the radiation emission path of the radiation emitter 10to pass radiation. In this case, since the opening 141 a is smaller thanthe opening 141 of the filter 14 as described above in FIG. 5D, it maybe necessary to reduce the angular speed of the filter 14 under theassumption of the same size of the irradiation zone. That is, the filter14 rotates by 180 degrees from a point (a) to a point (c) in the case ofFIG. 5D, but rotates by 90 degrees from a point (f) to a point (g) inthe case of FIG. 6B.

Starting from a point h where the filter 14 enters a next irradiationzone, the other opening 141 b is located on the radiation emission pathof the radiation emitter 10 to pass radiation.

As such, as illustrated in FIG. 6B, assuming that the filter 14 has thetwo openings 141 a and 141 b and the size of each opening is a quarterof the size of the disc, a rotational angular speed of the filter 14 isonly 1.5 times an angular speed of the radiation emitter 10. That is,the filter 14 rotates by a half rotational angular speed of that in theexemplary embodiment illustrated in FIG. 5D.

For example, if the non-irradiation zone is longer than the irradiationzone, that is, if an arc length of the non-irradiation zone is longerthan an arc length of the irradiation zone of FIG. 3B, the size of theopening 141 of the filter 14 may be less than the size of the blockingportion 142. In this case, as described above, the filter 14 may rotateby the same angular speed without requiring change in the angular speedof the filter 14.

Accordingly, the rotational speed of the filter 14 may be set based onthe number, size, or shape of the openings 141 of the filter 14.

FIGS. 7A to 7C are views illustrating various exemplary embodiments ofthe filter 14.

As illustrated in FIG. 7A, the filter 14 may be a semi-circular platesuch that the semi-circular blocking portion 142 blocks radiation.Similar to the above description, the filter 14 rotates about therotating shaft 143.

As illustrated in FIG. 7B, the filter 14 may take the form of acombination of a plurality of fan-shaped blocking portions 142. In thiscase, the plurality of fan-shaped blocking portions 142 may be spacedapart from one another, such that a plurality of openings 141 forpassage of radiation is present between the respective blocking portions142. The plurality of openings 141 may also have a fan shape. Similar tothe above description, the filter 14 including the plurality offan-shaped blocking portions 142 may rotate about the rotating shaft143.

As illustrated in FIG. 7C, at least one blade 142 may rotate about therotating shaft 143 that is horizontal to the blade 142 to pass or blockradiation.

In other exemplary embodiments, a filter may not have a completelyrotative movement and may have back and forth motion, reciprocatingmotion, or oscillatory motion. For example, the filter 14 in FIG. 5A andany other filters would rotate or move back and forth within an arc thatis less than 360 degrees, to act as a shutter in opening or closing apath through which the emitted radiation would pass.

As described above, the filter 14 may have various shapes, and anangular speed of the filter 14 may be set based on the shape of thefilter 14.

As occasion demands, other shapes of the filter 14 to pass or blockradiation may be applied to the radiation imaging apparatus.

According to an exemplary embodiment, the radiation imaging apparatusmay further include the cradle 61 on which the object ob may be placedas illustrated in FIG. 1. The cradle 61 may take the form of a table onwhich a human body may be placed according to exemplary embodiments. Ifthe radiation imaging apparatus is a computed tomography apparatus, thecradle 61 may move along a linear path.

If radiation is emitted to the object ob placed on the cradle 61, theradiation may be absorbed or reduced in transmittance by internaltissues or materials of the object ob according to properties of theinternal tissues or materials of the object ob, for example, accordingto an attenuation coefficient of the internal materials. The radiationhaving passed through the object ob or having passed around the objectob rather than reaching the object ob is received by the radiationdetector 20.

FIG. 8 is a view explaining emission of radiation to an object accordingto an exemplary embodiment.

As illustrated in FIG. 8, the object ob placed on the cradle 61 may notbe exposed to radiation in a direction opposite to a radiation emissiondirection.

That is, as illustrated in FIG. 8, if radiation, for example, X-rays isdirected to the object ob in a first direction, no radiation is directedto the object ob in an opposite direction, i.e. in a fourth direction.Similarly, if radiation is directed to the object ob in a third or fifthdirection, no radiation is directed to the object in a directionopposite to the third or fifth direction, i.e. in a sixth or seconddirection.

In the case in which radiation is emitted to the object ob in a givendirection, to ensure that no radiation is emitted to the object ob in adirection opposite to the given direction, it may be possible to controlvoltage to be applied to the radiation tube 11 of the radiation emitter10 as described above, and to control passage of radiation using thefilter 14 that is installed on a radiation emission path of theradiation emitter 10.

With the radiation imaging apparatus according to the exemplaryembodiments, radiation is emitted to the object ob on the cradle 61 in agiven direction, for example, in a first, third or fifth direction, andno radiation is emitted to the object ob in an opposite direction, forexample, in a fourth, sixth, or second direction. Accordingly, theobject ob is exposed to half as much radiation as compared to the casein which radiation is emitted to the object ob in all directions.

FIG. 9 is a view illustrating the radiation detector 20 according to anexemplary embodiment.

The radiation detector 20, as illustrated in FIG. 9, may be divided intoa plurality of pixels 21 to receive radiation. To receive radiation andchange the radiation into an electric signal, each pixel 21 may includea light receiving element, such as a scintillator 211, a photodiode 212,and a storage element 213.

The scintillator 211 receives radiation and outputs photons, inparticular, visible photons according to the received radiation. Thephotodiode 212 receives the photons output from the scintillator 211 andchanges the photons into an electric signal. The storage element 213 iselectrically connected to the photodiode 212 and stores the electricsignal output from the photodiode 212. In one exemplary embodiment, thestorage element stores the information represented by the electricalsignal. Here, the storage element 213, for example, may be a capacitor.The electric signal stored in the storage element 213 of each pixel 21,as illustrated in FIGS. 1 and 9, is read out by the image processor 30.As the image processor 30 generates a radiological image based on thereadout electric signal, the radiation detector 20 may acquire theradiological image corresponding to the received radiation.

After being subjected to desired image processing, the generatedradiological image, as illustrated in FIG. 1, may be connected to theradiation imaging apparatus via a wireless or wired communicationnetwork, such as a cable, or may be displayed to the user via a displaydevice D installed to the radiation imaging apparatus.

FIGS. 10A to 10C are a perspective view and explanatory views of acollimator installed to the radiation detector.

As illustrated in FIG. 10A, a second collimator 22 may be installed suchthat radiation having passed through the object reaches the secondcollimator 22 prior to reaching the radiation detector 20. The radiationmay be scattered as designated by x4 and x5 of FIG. 10B while passingthrough the object ob. Scattering of radiation causes the pixels toreceive incorrect positions of the scattered radiation, which maydeteriorate accuracy of a finally generated radiological image.

The second collimator 22, as illustrated in FIG. 10C, absorbs theradiation scattered by the object ob and causes appropriate radiation toreach the radiation detector 20, which improves accuracy of an image.

The radiation imaging apparatus may include the image processor 30 asillustrated in FIG. 1. FIGS. 11A and 11B are views illustrating aconfiguration of the image processor according to several exemplaryembodiments.

As illustrated in FIG. 11A, the image processor 30 according to oneexemplary embodiment may include an image generator 31, an imagecombiner 33, and an effect processor 34.

The image processor 30 simultaneously or sequentially reads out electricsignals stored in the respective storage elements 213 of the pixels ofthe radiation detector 20, thereby acquiring raw image data i requiredfor generation of a radiological image. The readout electric signals,i.e. raw image data i may be temporarily stored in a separate storagespace.

The raw image data i is not changed from radiation emitted in alldirections as described above with reference to FIGS. 3A to 8, but ischanged from radiation emitted only at a position or zone, i.e. withinan irradiation zone. That is, the raw image data I includes only imagedata in some of all directions, for example, in an irradiation zone, anddoes not include image data i′ in the other directions, for example, ina non-irradiation zone.

If the storage elements 213 of the radiation detector 20 may temporarilystore the electric signals transmitted from the photodiodes 212 wheneverradiation is emitted or may do not store the electric signalsrepeatedly, i.e. if it may be necessary to delete previously storedelectric signals from the storage elements 213 for storage of newlygenerated electric signals, the image processor 30 may read out theelectric signals from the storage elements 213 whenever radiation isemitted. If the storage elements 213 of the radiation detector 20 mayseparately store the electric signals generated whenever radiation isemitted, it may not be essential for the image processor 30 to read outthe electric signals whenever radiation is emitted.

The readout electric signals, i.e. raw image data i may be processed bythe image generator 31 of the image processor 30.

The image generator 31 may generate a radiological image based on rawimage data i. In this case, the image generator 31 may generate aradiological image such that pixels corresponding to the storageelements 213 in which respective electric signals are stored correspondto pixels constituting the radiological image.

If electric signals are read out from the storage elements 213 wheneverradiation is emitted as described above, the image generator 31 maygenerate a radiological image whenever the electric signals are readout.

If the radiation emitter 10 emits radiation having different energybands to the object ob, the image generator 31 may generate a pluralityof radiological images corresponding to the different energy bands. Byapplying weighting to the respective radiological images or viacombination or subtraction of the radiological images, a multi-energyradiological image may be generated.

The radiological image generated by the image generator 31 is notcaptured in all directions as described above in FIGS. 3A to 8, but is aradiological image captured when the radiation emitter 10 is located ina position or zone, i.e. in an irradiation zone.

FIGS. 12A to 12C are views respectively illustrating radiation emissionin different directions and radiological images acquired by radiationemission.

Referring to FIG. 12A, if radiation is emitted to a unit material e ofthe object ob, the radiation is attenuated while passing through theunit material e. More specifically, assuming that radiation x11 isemitted to the unit material e in a given direction, some of theradiation will be absorbed by the unit material e and some of theradiation will pass through the unit material e according to theconstitution of the unit material e. As such, radiation x12 havingpassed through the unit material e is attenuated as compared to theradiation x11 by a rate. In this case, the attenuation rate isdetermined according to the kind or density of the material. Likewise,if radiation x21 is emitted in a direction different from the aboveradiation emission direction, for example, in a direction opposite tothe above radiation emission direction as exemplarily illustrated inFIG. 12A, radiation X22 having passed through the unit material e isattenuated by the rate depending on the unit material e. In this case,if the radiation x11 emitted in a given direction and the radiation x21emitted in a different direction have the same magnitude, the radiationx12 and x22, which have been emitted in different directions and passedthrough the same unit material e, may have the same or very similarmagnitude due to the same attenuation rate. In this way, if theradiation x11 and x21 having the same magnitude are emitted to the sameunit material, the above-described radiation detector 20 acquires thesame radiation x21 and x22.

Referring to FIG. 12B, the object ob may consist of a plurality of unitmaterials. In this case, the respective unit materials, for example,first to fifth unit materials e1 to e5 have the same properties, andthus radiation having passed through the respective unit materials e1 toe5 has the same attenuation rate. For example, as exemplarilyillustrated in FIG. 12B, the radiation x12, which is acquired as theradiation x11 emitted to the object ob in a given direction passesthrough the plurality of unit materials e1 to e5, is equal to theradiation x22 which is acquired as the radiation x21 emitted in adirection corresponding to the given direction, for example, emitted inan opposite direction passes through the plurality of unit materials e1to e5. In this way, the same image may be acquired using the radiationx11 and x21 emitted in different directions, for example, in oppositedirections.

For example, as exemplarily illustrated in FIG. 12C, an eleventhradiological image ill, which is acquired by emitting radiation in aparticular position, for example, in an eleventh position 111, may beequal to a twenty first radiological image, which is acquired byemitting radiation in a position corresponding to the particularposition, for example, in a twenty first position 121. In this case, theparticular position, i.e. the eleventh position 111 and the position,i.e. the twenty first position 121 corresponding to the particularposition may be opposite to each other about the object ob.

Likewise, for example, twelfth to fourteenth radiological images i12 toi14, which are acquired by emitting radiation in twelfth to fourteenthpositions l12 to l14, may be equal to twenty second to twenty fourthradiological images i22 to i24 which are acquired by emitting radiationin twenty second to twenty fourth positions corresponding to the twelfthto fourteenth positions l12 to l14.

Accordingly, even if radiation is not emitted in the twenty first totwenty fourth positions l21 to l24, radiological images of the object obin all directions may be acquired using radiological images acquired byemitting radiation in the eleventh to fourteenth positions l11 to l14.

Consequently, as exemplarily illustrated in FIG. 3A or FIG. 4B, evenwhen radiation is emitted to the object ob only in positions or zones,rather than being emitted to the object ob in all positions or zones,substantially the same radiological image as that acquired by emittingradiation to the object ob in all positions or zones may be acquired.

Accordingly, the image generator 31 of the image processor 30 maysufficiently acquire images of the object ob in all directions usingonly radiological images in particular positions or zones.

This will now be described in more detail with reference to FIGS. 12D to12F. FIGS. 12D and 12E are views respectively illustrating a spatialdomain and a frequency domain acquired by the radiation imagingapparatus.

A spatial domain depending on radiation emission from the radiationimaging apparatus, for example, a computed tomography apparatus is asillustrated in FIG. 12D.

In FIG. 12D, if the radiation emitter 10 emits radiation at a positionθ, radiation having passed through the object ob reaches the radiationdetector 20. The radiation emitter 10 and the radiation detector 20 movealong respective movement paths thereof. In this case, the radiationemitter 10 emits radiation only within a range, i.e. within a range oran arc of −β to +β. That is, a relationship of −β≦θ≦+β is acquired.Through the above-described method, image data within a range for theobject ob, i.e. within an X-ray irradiation zone may be acquired.

This may also be represented using a frequency domain as illustrated inFIG. 12E.

An image captured in the position θ of FIG. 12D may be represented by adotted line (sampling area) within a fan of FIG. 12E. Since theradiation emitter 10 emits radiation only within a range, i.e. within arange of −β to +β, even in the case of a frequency domain, only datawithin a fan-shaped zone having a contained angle of 2β is acquired. Inthis case, as exemplarily illustrated in FIG. 12D, a plurality ofsymmetrical fan-shaped image data may be acquired from the frequencydomain.

A relationship between a spatial domain and a frequency domain may berepresented by the following Equations 2 to 4.

First, data acquired by emitting radiation in a given direction in thespatial domain may be defined by the following Equation 2.

P _(θ)(t)=∫∫f(x,y)δ(x cos θ+y sin θ−t)dxdy  Equation 2

Here, P_(θ)(t) is acquired radiation emission data, and x and y arecoordinates of an arbitrary unit material within the object. Inaddition, f(x, y) is data on the arbitrary unit material at thecoordinates (x, y) within the object. θ is a contained angle between anemission direction and the X-axis.

The above Equation 2 may be represented as the first line of thefollowing Equation 3, and the following Equation 4 may be acquired viacalculation of Equation 2 and Equation 3.

$\begin{matrix}\begin{matrix}{{P_{\theta}(\omega)} = {\int{{P_{\theta}(t)}^{{- j}\; 2\; \pi \; \omega \; t}{t}}}} \\{= {\int{\int{{f\left( {{{t\; \cos \; \theta} - {l\; \sin \; \theta}},{{t\; \sin \; \theta} + {l\; \cos \; \theta}}} \right)}^{{- j}\; 2\; \pi \; \omega \; t}\; {t}{l}}}}} \\{= {\int{\int{{f\left( {x,y} \right)}^{{- j}\; 2\; \pi \; {\omega {({{x\; \cos \; \theta} + {y\; \sin \; \theta}})}}}{x}{y}}}}}\end{matrix} & {{Equation}\mspace{14mu} 3} \\{{P_{\theta}(\omega)} = {F\left( {{\omega \; \cos \; \theta},{\omega \; \sin \; \theta}} \right)}} & {{Equation}\mspace{14mu} 4}\end{matrix}$

The above Equation 4 corresponds to the above-described frequencydomain. Accordingly, the spatial domain depending on emission ofradiation by the radiation emitter as exemplarily illustrated in FIG.12D may be represented as the frequency domain as exemplarilyillustrated in FIG. 12E.

Meanwhile, if radiation is emitted to the object ob only in a particularzone as exemplarily illustrated in FIG. 3A or FIG. 4B, data is acquiredin the frequency domain as exemplarily illustrated in FIG. 12F. That is,for example, if radiation is emitted in a first irradiation zone a1 ofFIG. 3B, data 1 may be acquired as exemplarily illustrated in (a) ofFIG. 12F. Subsequently, if radiation is emitted in a second irradiationzone a3, novel data 2 may be acquired as exemplarily illustrated in (b)of FIG. 12F. Likewise, if radiation is emitted in a third irradiationzone a5, novel data 3 may be additionally acquired as exemplarilyillustrated in (c) of FIG. 12F. Consequently, image data in the entireregion may be acquired as exemplarily illustrated in (c) of FIG. 12F.

As described above, the radiation imaging apparatus does not emitradiation to the object ob in a direction corresponding to a particularradiation emission direction, for example, in a direction opposite tothe particular direction, i.e. within a non-irradiation zone, andtherefore the radiation detector 20 does not detect any radiation.Accordingly, no image data is acquired in the non-irradiation zone.

Accordingly, by emitting radiation to the object ob only in somedirections, it may be possible to acquire the same image orsubstantially the same image as that acquired when emitting radiation inall directions while reducing radiation exposure of the object ob.

Meanwhile, the image combiner 33 may generate a new radiological imageby combining acquired radiological images or image data on theradiological images.

More specifically, the image combiner 33 may generate a successiveradiological image, for example, a panorama image or moving image byconnecting or combining radiological images generated by the imagegenerator 31.

The effect processor 34 performs desired image processing on aradiological image i1 generated by the image generator 31 or aradiological image generated by the image combiner 33, thereby improvingthe quality and readout efficiency of a radiological image to bedisplayed on the display device D. Here, desired image processing mayinclude, for example, post-processing including adjustment of color,brightness, contrast, or clarity of all or some of the generatedradiological images as well as removal of noise. The effect processor 34may perform the desired image processing on the generated radiologicalimage in response to user requests or based on predefined setting.

FIG. 11B is a view illustrating a configuration of the image processoraccording to another exemplary embodiment.

The image processor 30 of the present exemplary embodiment may furtherinclude a reverse image generator 32.

The reverse image generator 32 may generate, using a radiological imagecaptured in a particular direction, for example, a radiological imagecaptured in an irradiation zone, a radiological image captured in adirection corresponding to the particular direction, for example, in adirection opposite to the particular direction, for example, in anon-irradiation zone. Alternatively, the reverse image generator 32 maycalculate image data i′ related to an image captured in a directioncorresponding to a particular direction, thereby compensating forinsufficient image data for a radiological image, for example, atomographic image.

The reverse image generator 32 may generate and calculate, using theradiological image generated based on radiation emitted in theparticular direction or using the acquired image data I, an image in adirection corresponding to the particular direction, for example, in adirection opposite to the particular direction or image data i′ in adirection corresponding to the particular direction.

For example, the reverse image generator 32 may acquire a reverse imageby rearranging each data of a radiological image generated based onradiation emitted in a particular direction at a symmetrical positionabout a center line perpendicular to the particular direction.

According to exemplary embodiments, the reverse image generator 32 maygenerate a reverse image or reverse image data i′ by applying weightingto a part of a radiological image or image data i captured in aparticular direction.

Additionally, the reverse image generator 32 may generate or calculate asingle reverse image or reverse image data i′ by generating orcalculating new radiological images or image data based on a pluralityof radiological images or image data i captured in a plurality ofdirections, and thereafter combining the acquired radiological images orimage data. In this case, at least one reverse image may be acquired bycombining the plurality of radiological images, or by applying weightingto each of the plurality of radiological images, combining the resultingradiological images, and calculating a reverse image of the combinedimage.

In this case, the image combiner 33 may generate a successiveradiological image, for example, a panorama image or moving image byconnecting or combining radiological images generated by the imagegenerator 31 and the reverse image generator 32.

The image combiner 33 may combine image data i of at least oneirradiation zone acquired from the storage elements 213 with reverseimage data i of at least one non-irradiation zone calculated by thereverse image generator 32, thereby generating a radiologicaltomographic image for the cross section of the object ob to whichradiation is emitted.

The image generated by the image processor 30, as exemplarilyillustrated in FIG. 11A, may be transmitted to a storage unit 62 or thedisplay device D.

The storage unit 62, as exemplarily illustrated in FIG. 11, temporarilyor semi-permanently stores a radiological image in a particulardirection and a radiological image in a direction opposite to theparticular direction generated by the image processor 30, an imagegenerated by the image combiner 33 via combination of the aboveradiological images, or a radiological image generated by performingdesired post-processing on the above radiological images.

The display device D displays a radiological image generated by theimage processor 30 or stored in the storage unit 62 to a user, forexample, a doctor, nurse, radiologist, or patient. In an exemplaryembodiment, the display device D may be a monitor mounted to theradiation imaging apparatus, an external monitor connected to theradiation imaging apparatus via a wired or wireless network, or aninformation processing device, such as a computer, to which a monitor isconnected.

According to an exemplary embodiment, the radiation imaging apparatus,as exemplarily illustrated in FIG. 13, may be a computed tomographyapparatus 70.

FIG. 13 is a view illustrating a configuration of a computed tomographyapparatus.

As illustrated in FIG. 13, according to an exemplary embodiment, thecomputed tomography apparatus 70 includes a controller 71 to controlgeneral operations of the computed tomography apparatus 70, a gantrydrive unit 72 a to drive a gantry 72 upon receiving a controlinstruction output from the controller 71, a drive unit 73 a to drive acradle 73 upon receiving a control instruction output from thecontroller 71, a radiation emitter 721 and a radiation detector 722installed to the gantry 72 to emit radiation to the object ob, a gantrymotion measurement unit 76 to measure motion of the gantry 72, forexample, a movement angle of the gantry 72 to thereby transmit measuredinformation to the controller 71, and an image processor 74 to generatea radiological image of the object ob. The radiological image generatedby the image processor 74 is displayed to the user, for example, adoctor or radiologist via a display unit 75.

FIGS. 14 to 16 are views illustrating an exemplary embodiment of thecomputed tomography apparatus, and FIGS. 17 and 18 are views explainingradiography by the computed tomography apparatus.

Referring to FIG. 14, the computed tomography apparatus 70 may include ahousing 81 having a central bore 82, a cradle 73 to transfer the objectob placed thereon, and a support structure 83 to support the cradle 73.The cradle 73 that supports the object ob on an upper end thereof istransferred at a predetermined speed into the gantry 72 through the bore82 of the housing 81 under control of the cradle drive unit 73 a. Inthis case, the object ob placed on the upper end of the cradle 73 istransferred thereby.

According to an exemplary embodiment, the computed tomography apparatus70 includes an information processing device 84 that displays an imageof the object ob and receives various control instructions for thecomputed tomography apparatus 70 input by the user. The informationprocessing device 84 may include the display unit 75 to display aradiological image to the user, and the above-described controller 71.

Referring to FIGS. 13 to 16, the gantry 72 is installed within thehousing 81, and the radiation emitter 721 and the radiation detector 722are mounted to the gantry 72.

The gantry 72 is rotated by the gantry drive unit 72 a that is driven inresponse to a control instruction of the controller 71. The radiationemitter 721 and the radiation detector 722, mounted to the gantry 72,are fixed at positions facing each other, such that radiation emittedfrom the radiation emitter 721 may be detected by the radiation detector722. That is, the radiation detector 722 is installed to the gantry 72at a position opposite to the radiation emitter 721. A first collimator721 a is installed in a path along which the radiation emitter 721 emitsradiation, and serves to filter a radiation emission direction andradiation emission range that the user desires. A second collimator 722a may be installed in a path along which the radiation detector 722receives radiation and serves to block radiation scattered within theobject ob so as to improve accuracy of a radiological image.

If computed tomography is initiated, the gantry 72 initiates rotationaccording to revolutions per minute preset or input by the user via theexternal information processing device 84. The radiation emitter 721emits radiation to the object ob while rotating along with the gantry72. The radiation detector 721 detects radiation having passed throughthe object ob or directly reached thereto without passing through theobject ob while rotating along with the radiation emitter 721. Then, theradiation detector 721 changes the detected radiation into an electricsignal to store the electric signal in the storage element.

Meanwhile, if computed tomography is initiated, as exemplarilyillustrated in FIG. 16, the cradle 73 is transferred into the gantrythrough the bore 82. As such, the radiation emitter 721 emits radiationwhile being rotated by the gantry 72 relative to the moving object ob.

Accordingly, when viewed on the basis of the object ob, the radiationemitter 721 emits radiation to the object ob while moving along a spiralor a helical path as exemplarily illustrated in FIG. 17. Similarly, whenviewed on the basis of the object ob, the radiation detector 722 movesalong a spiral or a helical path according to movement of the radiationemitter 721.

The radiation emitter 721, as exemplarily illustrated in FIG. 18, may becontrolled to emit radiation to the object only in a direction, and soas not to emit radiation in a direction corresponding to the radiationemission direction, for example, in an opposite direction. For example,under control, the radiation emitter 721 may emit radiation to theobject in the particular position l1 as illustrated in FIG. 3A or in theparticular irradiation zone a1 as exemplarily illustrated in FIG. 3B,and may not emit radiation to the object ob in the position l4 oppositeto the particular position l1 or in the zone opposite to the irradiationzone a1, i.e. in the non-irradiation zone a4.

The radiation emitter 721 may be controlled by the above-describedcontroller 71.

As described above with reference to FIGS. 3C and 3D, the controller 71may control radiation emission by the radiation emitter 721 by applyingor not applying power to the radiation tube of the radiation emitter721. In other words, the controller 71 may control Power-On/Off of theradiation emitter 721.

To allow the radiation emitter 721 to emit radiation at a position orzone, according to an exemplary embodiment, the gantry motionmeasurement unit 76 may measure motions of the gantry 72. Specifically,the gantry motion measurement unit 76 may acquire information on aposition of the radiation emitter 721 by measuring a rotation angle ofthe gantry 72 from an initial position thereof. The gantry motionmeasurement unit 76 transmits information on the acquired position tothe controller 71, and the controller 71 generates a control instructionfor the radiation emitter 721 based on information on the acquiredposition to transmit the control instruction to the radiation emitter721, thereby allowing the radiation emitter 721 to emit radiation to theobject ob only at a position or zone.

As described above, radiation emitted by the radiation emitter 721 isdetected by the radiation detector 222 to thereby be changed into anelectric signal, and the image processor 74 reads out a radiologicalimage from the electric signal. As a result, a radiological image may beacquired by radiation emitted in a position or zone. Meanwhile, asdescribed above with reference to FIGS. 12A to 12F, even when aradiological image is acquired by emitting radiation only in a positionor zone, that is, even if the radiation emitter 721 does not emitradiation in a position or zone corresponding to the radiation emissionposition or zone, radiological images of the object ob in all directionsmay be acquired.

FIGS. 19 to 21 are views illustrating another exemplary embodiment ofthe computed tomography apparatus.

According to another exemplary embodiment of the computed tomographyapparatus 70, as illustrated in FIGS. 19 to 21, a filter 723 may beinstalled in a radiation emission direction of the radiation emitter721, i.e. in a path along which the radiation emitter 721 emitsradiation. The filter 723 controls emission of radiation to the objectob by passing or blocking the radiation from the radiation emitter 721.In particular, the filter 723 may pass or block radiation when theradiation emitter 721 is located at a position or zone.

The filter 723 may have various shapes as illustrated in FIGS. 5A to 5Dand FIGS. 6A and 6B. In particular, according to an exemplaryembodiment, the filter 723 may include at least one opening 141 to passradiation, and may rotate about the rotating shaft 143 located inside oroutside of the filter 723. A rotational angular speed of the filter 723is set to correspond to an angular speed of the radiation emitter 721that moves along a circular or spiral movement path. In addition, therotational angular speed of the filter 723 may be set, as describedabove, based on the number of openings 141 for passage of radiation, thenumber of times radiation is emitted while the radiation emitter 721moves along a circular movement path once, and the sizes of irradiationzones and non-irradiation zones.

Accordingly, as exemplarily illustrated in FIG. 21, despite that theradiation emitter 721 continuously emits radiation, the filter 723 maycause radiation to be emitted to the object ob only in some directionsby blocking radiation in a particular position or zone, in particular,in a position or zone opposite to the emission position or zone.

In the case of some conventional radiation tomography apparatuses, thegantry 72, i.e. the radiation emitter 721 acquires a radiological imageof 800 to 1400 frames while rotating for about 250 ms, and thereforethere is difficulty in controlling the radiation emitter 721 toperiodically emit radiation. This is because control of periodicgeneration of radiation may require application of a high voltage to theradiation emitter 721, more particularly to the radiation tube for 0.2μs.

However, when using the filter 723, emission of radiation to the objectob may be controlled even by continuously applying a voltage to theradiation emitter 721, rather than periodically applying a voltage tothe radiation emitter 721. In other words, emission of radiation to theobject ob may be controlled even in the case in which the radiationemitter 721 continuously generates radiation, rather than periodicallygenerating radiation.

In other words, as exemplarily illustrated in FIG. 3C, it may bepossible to control emission of radiation to the object ob in a pulseform.

Accordingly, a radiation tomography apparatus that may not controlperiodic generation of radiation may realize periodic emission ofradiation to the object ob.

Radiation, which has emitted by the radiation emitter 721 and passedthrough the filter 723, may be detected by the radiation detector 722and changed into an electric signal. The changed electric signal is readout by the image processor 74, and the image processor 74 generates aradiological image using the electric signal. Consequently, aradiological image may be acquired by radiation emitted in a position orzone. In this case, as described above with reference to FIGS. 12A to12F, although the radiation emitter 721 emits radiation only in aposition or zone, and does not emit radiation in a position or zonecorresponding to the position or zone, radiological images of the objectob in all directions may be acquired.

FIGS. 22A to 22C are views explaining generation of radiological imagesaccording to an exemplary embodiment.

As described above, radiation emitted from the radiation emitter 721 isdetected and changed into an electric signal by the radiation detector722, and the image processor 74 reads out a radiological image from theelectric signal. In this case, the image processor 74, as describedabove, may acquire radiological image data in a radiation emissiondirection as well as radiological image data in a directioncorresponding to the radiation emission direction. However, in a spiralor a helical scan method, since the object ob is moved in a direction,for example, in a transfer direction, radiological image data acquiredin a radiation emission direction may differ from radiological imagedata acquired in a direction corresponding to the radiation emissiondirection.

For example, as illustrated in FIGS. 22A and 22B, since the radiationemitter 721 emits radiation only in a position, for example, in aposition b1 or b3 or in a zone while spirally rotating about the objectob, image data for a first cross-section c1 in the position b1 or athird cross-section c3 in the position b3 may be acquired, but aradiological image in a non-irradiation position, for example, in aposition b2 or other positions, for example, accurate image data for asecond cross-section c2 may not be acquired.

According to an exemplary embodiment, as exemplarily illustrated in FIG.22C, an image t2 of the second cross-section c2 may be acquired using animage t1 of the first cross-section c1 and an image t3 of the thirdcross-section c3. In addition, radiological image data that will beacquired when radiation is emitted in the position b2 may be acquiredusing the image t2 of the second cross-section c2.

Image data on the second cross-section c2 may be acquired using anintermediate value between image data on the first cross-section c1 andimage data on the third cross-section c3, or by applying weighting toeach image data and combining the image data. In this case, an image ofthe second cross-section c2 may be acquired by comparing the image t1 ofthe first cross-section c1 and the image t3 of the third cross-sectionc3 with each other and using a motion prediction method.

A plurality of radiological images acquired as described above, forexample, a plurality of image data including image data on the firstcross-section c1, image data on the second cross-section c2 and imagedata on the third cross-section c3 are combined by the image processor74, whereby a cross-sectional image of the object ob is acquired and isdisplayed to the user via the display unit 75. Accordingly, aradiological tomographic image without data loss may be acquired evenvia radiation emission within a partial zone, i.e. an irradiation zone.

In another exemplary embodiment, the radiation imaging apparatus may bea Full Field Digital Mammography (FFDM) apparatus as exemplarilyillustrated in FIG. 23.

FIGS. 23 to 25 are views explaining an exemplary embodiment of the FFDMapparatus.

As exemplarily illustrated in FIGS. 23 and 24, the FFDM apparatus mayinclude a head m10 to which a radiation emitter m11 is installed, acradle m13 on which the object ob, for example, the breast is placed,and a compressor m12 to compress the object ob, for example, the breast.

The radiation emitter m11, installed to the head m10, may emit radiationtoward the cradle m13. In one exemplary embodiment, the head m10, asexemplarily illustrated in FIG. 24, may be moved in at least onedirection along a movement path that is formed on a transfer device,such as a rail m14. In this case, the radiation emitter m11 installed tothe head m10 may be moved simultaneously with movement of the head m10.

The movement path of the head m10 may be divided into a plurality ofzones. The plurality of zones may be any one of an irradiation zone anda non-irradiation zone. The radiation emitter m11 emits radiation to theobject ob in the irradiation zone, and does not emit radiation to theobject ob in the non-irradiation zone by stopping emission of radiationby the radiation emitter m11.

In one exemplary embodiment, the plurality of zones may be arranged suchthat one irradiation zone corresponds to one non-irradiation zone. Inaddition, a zone corresponding to a non-irradiation zone among theplurality of zones may be an irradiation zone. For example, asexemplarily illustrated in FIG. 25, an irradiation zone and anon-irradiation zone may be symmetrical to each other about an axis, forexample, the Y-axis.

The compressor m12 may compress the object ob, for example, the breast,to ensure radiation of emission to a greater area of the object ob.

The object ob, for example, the breast is placed on the cradle m13. Thecradle m13 may further include a radiation detector to detect radiationemitted from the radiation emitter m11. The radiation detector mayinclude a radiation detection panel. The radiation detector may beinstalled inside or outside of the cradle m13, and may be installed, forexample, to an outer surface of the cradle m13 on which the breast isplaced.

Referring to FIGS. 24 and 25, the radiation emitter m11 of the FFDMapparatus may emit radiation to the object ob only in a zone, forexample, in an irradiation zone, and may not emit radiation to theobject ob in another zone, for example, in a non-irradiation zone. Inthis case, if the radiation emitter m11 is located in the irradiationzone, as described above, a voltage is applied to the radiation tube ofthe radiation emitter m11 (power-on state), whereby the radiationemitter m11 emits radiation to the object ob. In addition, if theradiation emitter m11 is moved to enter the non-irradiation zone, avoltage is no longer applied to the radiation tube of the radiationemitter m11 (power-off state), whereby the radiation emitter m11 stopsemission of radiation. If the radiation emitter m11 again enters theirradiation zone, a voltage is again applied to the radiation tube ofthe radiation emitter m11 (power-on state), whereby the radiationemitter m11 restarts emission of radiation.

In one exemplary embodiment, if radiation is emitted only in anirradiation zone, radiological image data only in the irradiation zonemay be acquired, but acquisition of radiological image data in thenon-irradiation zone may be impossible.

In this case, in one exemplary embodiment, radiological image data inthe non-irradiation zone may be calculated based on radiological imagedata in the irradiation zone by the above-described reverse imagegenerator 32. In addition, it may be possible to acquire radiologicalimage data in all zones by combining radiological image data in theirradiation zone with the calculated radiological image data in thenon-irradiation zone. In this way, it may be possible to generate animage of the object ob using the acquired radiological image data.

FIGS. 26 and 27 are flowcharts illustrating various exemplaryembodiments of a radiological image generation method.

As exemplarily illustrated in FIG. 26, according to an exemplaryembodiment of a radiological image generation method using a radiationimaging apparatus, for example, a computed tomography apparatus, ifradiation imaging is initiated, an object ob is placed on a cradle andis moved through a bore of the computed tomography apparatus. Inaddition, rotation of a gantry is initiated. A radiation emitter ismoved via rotation of the gantry (s90).

If the radiation emitter reaches an irradiation zone via movementthereof (s91), the radiation emitter begins to emit radiation to theobject (s92). In this case, a non-irradiation zone is located oppositeto the irradiation zone.

If the emitted radiation reaches a radiation detector after passingthrough the object, the radiation detector detects the radiation andchanges the radiation into an electric signal. The electric signal orthe image represented by the electrical signal is stored as image dataon the irradiation zone (s93). In this case, as described above withreference to FIGS. 12A to 12F, a radiological image in the irradiationzone as well as a radiological image in a corresponding non-irradiationzone may be acquired.

The radiation emitter continuously emits radiation while being moved toacquire data on a plurality of images. Then, if the radiation emitterreaches the non-irradiation zone, the radiation emitter stops emissionof radiation (s94). The non-irradiation zone is a zone corresponding tothe irradiation zone. For example, the non-irradiation zone may belocated symmetrical to the irradiation zone about a point or axis.

Through rotation of the gantry, Operations s90 to s94 are repeated toacquire image data in all zones (s95).

Radiological images in all directions are acquired using image dataacquired based on radiation emitted in all zones (s96). According toexemplary embodiments, based on image data acquired by emittingradiation in a particular direction, a reverse image may be acquiredusing data on an image captured in a direction opposite to theparticular direction (s96). That is, based on image data acquired in theirradiation zone, an image of the non-irradiation zone corresponding tothe irradiation zone may be acquired.

Meanwhile, in the case of using a spiral or a helical scan method, aradiological image in a non-irradiation zone corresponding to anirradiation zone may differ from a radiological image acquired byradiation emitted in the non-irradiation zone. In this case, asexemplarily illustrated in FIG. 27, a radiological image in thenon-irradiation zone may be calculated using a radiological imageacquired by emitting radiation in the irradiation zone.

According to an exemplary embodiment, first, at least two imagesacquired via radiation emission in the same direction are selected fromamong image data in the plurality of irradiation zones (s961). In thiscase, although the two image data may be images acquired by emittingradiation in the same radiation emission position or zone, it may beunnecessary to emit radiation in the same direction.

Then, intermediate image data is acquired by taking an intermediatevalue of the two image data or by applying weighting to the two imagedata and combining the two image data (s962). The intermediate imagedata, for example, may be data on the image t2 of the secondcross-section c2 as exemplarily illustrated in FIG. 22C.

At least one image data in a direction opposite to the radiationemission direction is calculated based on the acquired intermediateimage data (s963). As described above, since there is non-emissionopposite to the irradiation zone, a reverse image may not be acquiredvia radiation emission. In addition, in the case of a computedtomography apparatus, this is similar to the case in which the radiationemitter emits radiation to the object while spirally moving around theobject, and therefore a more accurate reverse image may be acquired whencalculation of intermediate image data proceeds.

As is apparent from the above description, through a radiation imagingapparatus, a computed tomography apparatus, and a radiation imagingmethod, it may be possible to acquire radiological images in alldirections of an object even when emitting radiation in some directionsor zones.

Even when a radiation emitter emits radiation in a pulse form, or evenwhen the object is irradiated in a pulse form, not only data on an imageof a partial angular range in which radiation emission is performed, butalso data on radiological images in all directions in which radiationemission is not performed, may be acquired, which provides sufficientradiological image data.

Accordingly, it may be unnecessary to directly emit radiation to theobject in all directions, which may allow the object, in particular, ahuman body to be exposed to less radiation. In particular, it may bepossible to reduce radiation exposure of the object by half in adirection opposite to a radiation emission direction as radiation is notemitted to the object in the direction opposite to the radiationemission direction.

In a computed tomography apparatus, it may be possible to generate asuccessive cross-sectional image of the object even if radiation isemitted in positions or zones.

Although the exemplary embodiments have been shown and described, itwould be appreciated by those skilled in the art that changes may bemade in these exemplary embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

What is claimed is:
 1. A radiation imaging apparatus comprising: aradiation emitter configured to emit radiation toward an object and tomove around the object at a same time; a radiation detector configuredto detect the radiation emitted from the radiation emitter, to changethe detected radiation into a signal, and to store the signal; and anirradiation controller configured to control the radiation emitter sothat the radiation is emitted toward the object in a first positionaround the object and so that no radiation is emitted toward the objectin a second position corresponding to the first position.
 2. Theapparatus according to claim 1, wherein the irradiation controllercontrols the radiation emitter so that the radiation emitter emits theradiation toward the object if the radiation emitter is located in thefirst position and so that the radiation emitter stops emitting theradiation if the radiation emitter is located in the second positionthat is opposite to the first position.
 3. The apparatus according toclaim 1, further comprising an image processor configured to read out aradiological image from the signal.
 4. The apparatus according to claim3, wherein the image processor generates at least one radiological imagecaptured based on a single radiological image captured in a radiationemission direction.
 5. The apparatus according to claim 1, wherein theradiation emitter moves about the object at an angular speed.
 6. Theapparatus according to claim 5, wherein the irradiation controllerdetermines whether or not the radiation emitter is to emit the radiationbased on the angular speed of the radiation emitter to generate adetermination result, and controls the radiation emitter based on thedetermination result.
 7. The apparatus according to claim 6, wherein theirradiation controller controls the radiation emitter so that theradiation emitter stops emitting the radiation when an irradiationduration has passed after the radiation emitter started to emit theradiation, and so that the radiation emitter restarts emitting theradiation after a non-irradiation duration has passed since theradiation emitter has stopped emitting the radiation.
 8. The apparatusaccording to claim 1, further comprising a filter disposed in aradiation emission path along which the radiation is emitted by theradiation emitter, to pass or to block the radiation emitted from theradiation emitter.
 9. The apparatus according to claim 8, wherein theirradiation controller controls the filter so that the filter passes theradiation emitted from the radiation emitter if the radiation emitterreaches the first position while moving about the object and so that thefilter blocks radiation emitted from the radiation emitter if theradiation emitter reaches the second position opposite to the firstposition about the object.
 10. A radiation imaging apparatus comprising:a radiation emitter configured to move along a path about an object in amovement and to emit radiation toward the object during the movement;and a radiation detector configured to receive the radiation emittedfrom the radiation emitter and to change the received radiation into asignal, wherein the path about the object is divided into at least oneirradiation zone in which the radiation emitter emits the radiation, andat least one non-irradiation zone in which the radiation emitter doesnot emit the radiation, and the at least one non-irradiation zone islocated opposite to the at least one irradiation zone.
 11. The apparatusaccording to claim 10, further comprising an image processor configuredto generate a radiological image by combining at least one radiologicalimage generated via detection of the radiation emitted in the at leastone irradiation zone.
 12. The apparatus according to claim 11, whereinthe image processor generates a radiological image of thenon-irradiation zone opposite to the at least one irradiation zone basedon the radiological image of the at least one irradiation zone.
 13. Theapparatus according to claim 10, wherein the at least one irradiationzone and the at least one non-irradiation zone are determined by an arcbetween at least two positions on the path.
 14. The apparatus accordingto claim 10, wherein the at least one irradiation zone and the at leastone non-irradiation zone on the path are alternatingly arranged.
 15. Theapparatus according to claim 10, wherein the radiation emitter is movedalong the path defined about the object at an angular speed.
 16. Theapparatus according to claim 10, further comprising an irradiationcontroller to control the radiation emitter so that the radiationemitter emits the radiation at the at least one irradiation zone and theradiation emitter stops emitting the radiation at the at least onenon-irradiation zone.
 17. The apparatus according to claim 16, whereinthe radiation emitter moves along the path about the object at anangular speed, and the irradiation controller determines whether or notthe radiation emitter is to emit the radiation based on the angularspeed of the radiation emitter to generate a determination result, andcontrols the radiation emitter based on the determination result. 18.The apparatus according to claim 17, wherein the irradiation controllercontrols the radiation emitter so that the radiation emitter stopsemitting the radiation when an irradiation duration has passed after theradiation emitter started to emit the radiation, and so that theradiation emitter restarts emitting the radiation after anon-irradiation duration has passed since the radiation emitter hasstopped emitting the radiation.
 19. A radiation imaging apparatuscomprising: a radiation emitter configured to move along a first pathabout an object and to emit radiation toward the object; a filterdisposed in a second path along which the radiation is emitted by theradiation emitter, to pass or to block the radiation emitted from theradiation emitter; and a radiation detector configured to receive theradiation emitted from the radiation emitter and to change the receivedradiation into a signal, wherein the filter passes the radiation emittedfrom the radiation emitter in at least one irradiation position orirradiation zone on the first path, and blocks the radiation emittedfrom the radiation emitter in at least one non-irradiation position ornon-irradiation zone corresponding to the at least one irradiationposition or irradiation zone.
 20. The apparatus according to claim 19,further comprising an image processor configured to read out aradiological image from the signal in the at least one irradiationposition or irradiation zone.
 21. The apparatus according to claim 20,wherein the image processor generates a radiological image of the atleast one non-irradiation position or non-irradiation zone based on theradiological image of the at least one irradiation position orirradiation zone.
 22. The apparatus according to claim 19, wherein theat least one irradiation position or irradiation zone and the at leastone non-irradiation position or non-irradiation zone on the first pathare alternatingly arranged.
 23. The apparatus according to claim 19,wherein the first path around the object is circular or spiral.
 24. Theapparatus according to claim 19, wherein the filter comprises at leastone opening to pass radiation.
 25. The apparatus according to claim 19,wherein the filter rotates about a shaft located inside the filter oroutside of the filter.
 26. The apparatus according to claim 25, whereinthe filter rotates at an angular speed corresponding to an angular speedof the radiation emitter that moves along a circular movement path or aspiral movement path.
 27. The apparatus according to claim 26, whereinthe angular speed of the filter is determined based on a number ofopenings formed in the filter to pass the radiation, the angular speedof the radiation emitter, a number of times radiation is emitted duringone rotation of the radiation emitter, or a size of the irradiation zoneor a size of the non-irradiation zone.
 28. A radiological imageacquisition method using a computed tomography apparatus, the methodcomprising: performing a radiation imaging operation to acquire aplurality of radiological image data in a plurality of directions bycontrolling a radiation emitter so that radiation is emitted toward anobject in at least one direction around the object and so that noradiation is emitted toward the object in a direction corresponding tothe at least one direction; and performing an image data combinationoperation to combine the plurality of radiological image data in theplurality of directions.
 29. The method according to claim 28, whereinthe radiation imaging operation includes: acquiring image data in an atleast one irradiation position or irradiation zone by emitting radiationtoward the object when the radiation emitter reaches the at least oneirradiation position or irradiation zone; stopping radiation emissionwhen the radiation emitter reaches at least one non-irradiation positionor non-irradiation zone; and acquiring the plurality of image data in aplurality of irradiation positions or irradiation zones by repeating theacquiring of the image data and the stopping of the radiation emission,and wherein the at least one irradiation position or irradiation zone islocated to correspond to the at least one non-irradiation position ornon-irradiation zone.
 30. The method according to claim 28, wherein theradiation imaging operation includes: passing radiation emitted towardthe object through the filter when the radiation emitter reaches the atleast one irradiation position or irradiation zone; and blockingradiation emitted toward the object, by the filter when the radiationemitter reaches the at least one non-irradiation position ornon-irradiation zone, and wherein the at least one irradiation positionor irradiation zone is located to correspond to the at least onenon-irradiation position or non-irradiation zone.